Jonathan E. Maddison Photo

Jon is a member of the firm's State Tax Group. He counsels multinational corporations on state and local tax, particularly the intersection of federal and state law on sales and use tax and income tax. Jon analyzes state tax policy and legislation and advises on the constitutionality of proposed legislation and regulations.

Jon also represents clients in state and local tax controversy and litigation matters, from audit to appeal. As a constitutional law adviser, he has filed amicus briefs in the U.S. Supreme Court on behalf of taxpayer trade associations. His clients include leaders in ecommerce and the digital economy.

Jon is a frequent author and commentator on constitutional law issues and appellate matters in state and local tax.


  • University of Pennsylvania Law School, 2013, J.D., Executive Editor, University of Pennsylvania Journal of Constitutional Law
  • Rutgers University, 2010, B.A., Political Science, summa cum laude

  • Pennsylvania
  • District of Columbia

  • Law360 Editorial Advisory Board, State and Local Tax

Notable Quotes

  • 5 August 2019 “Kansas Outlier Remote Seller Rules Could Face Challenge” Tax Notes 
  • 17 May 2019 “Wayfair and Marketplace Issues Dominate Discussion a Year Later “ Tax Notes
  • 14 May 2019 “Supreme Court Again Overturns Precedent in Ruling for States” Tax Notes 
  • 17 December 2018 “2019: The Year of Marketplace Legislation” Tax Notes
  • 21 November 2018 “Justices’ Lean Toward States’ Rights Boosts Taxing Powers” Law360
  • 9 October 2018 “New Jersey Governor Signs GILTI, Marketplace Bills” Tax Notes
  • 28 June 2018  "Sales Tax Decision Looms Large In Justice Kennedy's Legacy" Law360
  • 22 June 2018 "States Expected to Move Quickly to Enforce Remote Seller Laws" Tax Notes 
  • 22 June 2018 "U.S. Supreme Court Overturns Quill, Freeing States to Tax Online Sales" Tax Notes 
  • 7 June 2018 "4 Important State Tax Cases That Are Not Wayfair" Law360
  • 22 May 2018 "States Could Challenge restrictions on Taxing Authority After Gambling Decision" Tax Notes 
  • 16 May 2018 "Connecticut Legislature Approves Marketplace Bill" Tax Notes
  • 9 May 2018 "Iowa Republicans Pass Tax Reform Plan" Tax Analysts
  • 28 March 2018 "Online Retailers Urge Justices Not To Overturn Quill" Law 360
  • 19 January 2018 "States Mulling Marketplace Provider Laws for 2018" Bloomberg BNA 
  • 17 January 2018 "Sales Tax Collections Hanging on Mass. Rule, SCOTUS Ruling" The Boston Globe 
  • 16 January 2018 "Shock, Surprise, and Hope as Supreme Court Agrees to Revisit Quill" Tax Notes
  • 15 January 2018 "Justices Likely To Set New Tax Standard For Remote Vendors" Law 360 
  • 18 December 2017 "The SALT Cases of 2017" State Tax Notes
  • 4 October 2017 "South Dakota Petition Urges U.S. Supreme Court to Kill Quill" Tax Notes
  • 20 September 2017 "South Dakota Digital Tax Case Puts Retailers in ‘Tricky Spot’" Bloomberg BNA
  • 15 September 2017 "South Dakota High Court Finds Remote Sales Tax Law Unconstitutional" Tax Notes
  • 30 August 2017 "South Dakota High Court Should ‘Weigh In’ on Quill Overturn, State Argues" Tax Notes
  • 18 August 2017 "New Seattle Tax on Rich May Lead to Statewide Income Tax" Law 360
  • 31 July 2017 "Massachusetts DOR Proposes Remote Sales Tax Collection Reg" Tax Notes
  • 18 July 2017 "Last-Minute Provision in Ohio Budget Not 'Cookie Nexus,' Drafter Says" Tax Notes
  • 10 July 2017 "Litigation Likely for Washington Law Pushing Marketplaces to Collect Sales Taxes" Tax Notes
  • 5 June 2017 "Minnesota Marketplace Law Ripe for Legal Challenge" Bloomberg BNA
  • 5 June 2017 "Minnesota Enacts Nation's First Marketplace Nexus Provision" Tax Notes
  • 23 May 2017 "U.S. Supreme Court Denies Cert in State Tax Retroactivity Cases" Tax Notes
  • 22 May 2017 "Retroactive Tax Laws Muddying Businesses’ Future Decisions" Law 360
  • 6 April 2017 "Resurgence Of Tax On Receipts May Hurt State Economies" Law360
  • 5 April 2017 "Massachusetts to Require Remote Retailers to Collect and Remit Sales Tax" Tax Notes
  • 22 February 2017 "U.S. Supreme Court Declines to Hear 2 Dormant Commerce Clause Cases" State Tax Today
  • 2 February 2017 “Gorsuch May Bring Change to Tax on Out-of-State Sales” Law360
  • 8 December 2016 “Court Upholds Commercial Activity Tax” Accounting Today
  • 21 November 2016 “Ohio High Court’s Nexus Decision Highlights Need for Clarity From U.S. Supreme Court, Experts Say” State Tax Today
  • 17 November 2016 “Physical Tie Test for State Tax Takes Hit in Ohio” Law360
  • 16 November 2016 “Colo. Tax Reporting Row Unlikely to Nix Physical Tie Rule” Law360
  • 17 June 2016 “7 Tips for Simplifying Tax Writing” Law360
  • 29 May 2016 “Fla. Retailers Could Face Double Tax on Out-of-State Sales” Law360
  • 27 May 2016 “Tax on Florist’s Out-of-State Sales is Constitutional, Florida Supreme Court Holds” State Tax Today
  • 29 February 2016 “Direct Marketing v. Brohl and Advent of New Nexus Rules” Law360
  • 18 May 2015 “High Court Levels Individual, Corporate Taxes in Md. Ruling” Law360
  • 20 April 2015 “DMA Briefing Order Raises Questions on Comity, Quill, and CSX” State Tax Today
  • 9 April 2015 “High Court May Take Narrow Path in Md. Tax Case” Law360